合成碳氢化合物航空润滑油(SHALOs)在高温下随时间逐渐降解,导致它们的组成和性能在整个使用寿命内发生变化。因此,通过在分子水平上阐明机理来理解SHALO降解特性,作为高温的函数,是感兴趣的。将SHALO在180、200、230、250、270或300°C下进行热处理(TT)2h。通过傅立叶变换红外F光谱分析了六个TT样品和一个新鲜油的化学成分,高级聚合物色谱,和气相色谱/质谱。此外,物理化学性质,如运动粘度,倾点,和酸值,确定了七个样品。使用统计学方法通过聚类分析(CA)对油样进行分组。SHALO被确定为包含20个官能团,包括梳状烷烃,长链二酯,胺,酚类物质,和其他化合物。在<230°C下的TT导致SHALO基础油部分裂解,随着抗氧化剂含量和类型的变化,缩聚反应占主导地位。在>230°C下,从TT观察到的抗氧化剂变化不明显。检测到大量的小分子化合物,包括正构烷烃和烯烃。在250°C下的TT被证明是运动粘度的重要阈值,倾点,和样品的酸值。低于250°C,样品性能相对稳定;但在升高的TT温度(>250°C)下,观察到性能急剧降低。由于样品颜色对温度高度敏感,TT温度引起快速和显著的颜色变化。在分子水平上对油化合物的CA分析结果与在宏观水平上观察到的物理化学性质的变化非常吻合。
Synthetic hydrocarbon aviation lubricating oils (SHALOs) gradually degrade over time when subjected to high temperatures, resulting in their composition and properties varying over the operation lifetime. Therefore, understanding the SHALO degradation properties by elucidating the mechanism on a molecular level, as a function of high temperature, is of interest. A SHALO was subjected to thermal treatment (TT) at 180, 200, 230, 250, 270, or 300 °C for 2 h. The chemical compositions of six TT samples and one fresh oil were analyzed by fourier transform infrared F spectroscopy, advanced polymer chromatography, and gas chromatography/mass spectrometry. Furthermore, the physicochemical properties, such as kinematic viscosity, pour point, and acid number, of seven samples were determined. The oil samples were grouped by cluster analysis (CA) using a statistical method. The SHALO was identified to comprise 20 functional groups, including comb-like alkanes, long-chain diesters, amines, phenols, and other compounds. TT at <230 °C caused partial cracking of the SHALO base oils, with a concomitant change in the antioxidant content and type, and the polycondensation reactions were dominant. The observed antioxidant changes were not obvious from TT at >230 °C. A large number of small-molecule compounds were detected, including n-alkanes and olefins. TT at 250 °C was shown to be an important threshold for the kinematic viscosity, pour point, and acid number of the samples. Below 250 °C, the sample properties were relatively stable; but at elevated TT temperatures (>250 °C), the properties were observed to dramatically degrade. As the sample color was highly sensitive to temperature, the TT temperature induced rapid and significant color changes. The CA analysis results for the oil compounds at the molecular level were in good agreement with observed changes in the physicochemical properties at the macro level.